Every summer it happens, and every summer I take little steps to address it. I'm installing a WRX STi heat extractor in the hood, so I have a 18"X8" rectangle cut into the metal. I'm waiting for the adhesive fastening the fiberglass extractor onto composite hood piece to finish drying. I also removed the heat shielding on the inside of the hood. I have 2 electrics fans in place, one in front of the radiator, one behind the radiator (to eliminate the fan clutch as the cause). Thermostat has been replaced, as well.
Yesterday I was sitting in a bit of traffic, and the temp was in the 90s, so I turned the a/c on full blast to see if the vented hood would help alleviate the overheating. After about 5 mins, the familiar creep began again. Turned the a/c off, temp, once again, went back to normal.
Only happens when the a/c is on. I can sit in traffic w/out it, and it behaves just fine. I recalled this thread: http://vehicross.info/forums/showthread.php?t=20464 I'll be contacting them about a kit early next week. I'm pretty much done w/the heat issues.